8. Blue-ringed octopus

There are about four species of blue-ringed octopus around the Australian coast. They are normally brown and innocuous looking, but when disturbed, iridescent blue lines and rings appear.

Almost all bites have occurred when the octopus was picked up and taken out of the water, Robinson said. The simple message is: don't touch them and you'll be fine.

Danger rating: 7/10

Scientific name: Genus Hapalochlaena

How to know if it's got you: Once bitten by this octopus, symptoms can appear within minutes, depending on where you've been bitten. Because it contains neurotoxins, the body starts to shut down and becomes increasingly paralysed. Usually victims die because they stop breathing, Robinson added.